Hey guys. Been awhile since i posted here needing help. I have this chainsaw, it's a 365 special, that's a buddy of mine. He wanted it rebuilt once i had it here for some other repairs. While it's apart i figured id grind a little to learn a little. I'll be able to pull it apart and grind more if need be. I work with the guy. Is anyone here familiar with port numbers and what not? I have a degree wheel and other tools. I just need someone to bounce ideas off on this particular saw. Basically i have some ideas but don't know how viable they are and don't just wanna dive in head first with no plan. Im gonna need someone to make me feel stupid. Lol
If you don’t have tools to raise the upper transfers, I wouldn’t raise the exhaust. You could widen the exhaust to 65% of the bore and match the lower transfers to the case using the gasket as a template. And get the intake floor flat across at 78 or so. Should be able to delete the base gasket. Check squish clearance with 1mm soft electrical solder. You’d want .019”+ to delete it
I would have to agree and i don't expect anyone to just give up some numbers but was looking for someone to lead me in the right direction. Here are the numbers i got from the stock jug and piston before teardown with the base gasket installed. Now I've already bought a Highway Titanikel cylinder and piston kit. Its a 52mm kit. Now admittedly i kinda though that just throwing a bigger piston in would make more power, ya know, like 4 strokes. Now i see that i may have some extra work to do. I have the aftermarket p&c on there now but haven't written any numbers down yet. First thing i noticed though is the upper transfers are cast too low in the cylinder. So they only open up half way. Like i said, i don't have numbers yet but it's not looking good. Intake and exhaust look workable but I'm already worried about the amount of blow down this cylinder is capable of. That's for the intake number but i would venture to ask why you say 78°. I would kinda think duration would determine when to close the intake. While we are on the intake side. I noticed on the stock p&c that the top of the intake port is lower than the bottom of the piston at TDC. Would it be beneficial to raise the intake to match the bottom of the piston at TDC. I obviously have more questions but I'll see what yall have to say about that before i muddy the waters much more.
You have your wheel at 0 with the piston seemingly at tdc. I figured you were going by when the port opened from tdc rather than duration. Either way, 78+78 = 156° of duration on the intake No need to mess with the intake roof. It’ll slow down the velocity and doesn’t do any good sending the charge uphill when it all has to come down into the transfers anyway.
How about the upper transfers being cast too low in the cylinder? Can i get a good blow down number with grinding on them? Also would performance be hindered with the transfers on the new jug only opening half way? I realize I'm getting a little ahead of myself with talking numbers on this new cylinder with without writing down all the port opening/closing degrees. I'll get that done this evening and posr the numbers.
It’s definitely not great having them that low. When you make a port taller you lose velocity, and having more of it open below the top of the piston creates some turbulence. But most cylinders are like that. I don’t really know the reason why. As far as the big bore cylinder goes, it’s probably not going to run much better than your 48 MM cylinder unless you’ve ported enough of them to know exactly what they need to look like. Many people get hung up on displacement always winning, but it’s truly not the case here, at least not for me. Your results may be different. I’ve never had a problem making a 365 run well enough to where I would want to replace it with a 372 cylinder
Your wheel is better for checking durations than port openings from top dead center. In order to use your wheel to find duration, zero the wheel where the piston starts to crack the exhaust port open and then roll the motor over until the piston comes back up and closes the port off. And check your number there. Your wheel will show you the port time in duration. If you want a wheel better suited for checking port open from top dead center timing, get a wheel that goes up to 180 and then back down to zero, as opposed to yours going from 0–360°
I had Kevin port me a 365 special after much trigger time on one that Mike L. ported for my son. I love the platform. Those original cylinders run awesome after the proper work has been done to them.
Why not just do the math instead of having 2 different degree wheels? I'm pretty sure you can figure out duration of the ports that way. That's kinda why i posted my numbers. I was hopefully someone would actually look at them and see if they made sense. Doesnt seem to be the case yet though. I guess I'm looking for someone to talk 2 stroke principles and such. I've read quite a bit over on ope forums. They have a bunch of threads over there talking about each port and how they function and affect the other ports but nothing specific to this saw. I was hopeful that i could find some people here similarly minded to bunce some ideas off and maybe school me on others but it's kinda looking like I'm gonna have to start an account over there. Thanks for the info huskihl but i have a hard time following directions if you can't explain why. ✌️ Unfortunately the stock p&c is trash. Hence the new aftermarket one.
Yea i see you guys here are more into other things than modding chainsaws or power equipment. Figured I'd give yall a try since I'm already a member here. If anything came out or across as offensive.... my apologies. Like I've said, it's a project for my buddy and i just wanna do it write. Id buy what i need in order to make this cylinder right, ie. a foredom and carbide bits. I'll be able to pull this saw apart and grind more if need be or even throw this cylinder away once i grind on it and it doesn't work. I'm looking to learn something new cause i might have a couple saws i wanna mod for myself and actually i have a 353 I've ground on some just haven't moved the timing of the ports yet. It's not like I'm trying to start a business porting chainsaws. That would get old after about a month straight. I'm just trying to tinker around with my own stuff and friends stuff and not totally screw the pooch in the process. Then again I'm not looking at putting in work and not seeing a noticable gain. Anyway i just seem to be rambling. You guys have a good one.
Offensive? Nah.. I was just trying to get you to the right place for advice. Not a lotta saw modders here. Over there is a different story.
Guys over think a good woods port BIG TIME. You dont need 200 psi, you dont need finger ports and you dont need to move a lot of metal.... Especially in a Husky. One of my favorite saws that I own has almost nothing done to ports, but has about 20 degrees duration added by taking it out of the intake skirt lol. From your numbers, you already have a good number if you can get your intake closer to 80 (its at 69 from what I saw) and you can either start grinding on that intake port or you can just mark it on the skirt with it in the saw and take that amount off of the piston.
When you bore a 4-stroke, that's all you're changing, the compression system. When you change/modify pistons or cylinders in a piston-ported 2-stroke, even without changing the bore, it's the equivalent of changing the cam, valve size, crank throw, bore, compression, port/runner volume (intake mainfold & head) etc. 4-strokes are a good bit more "modular" for sure.
